Experimental investigation on strain rate effects of saturated clay subjected to freeze-thaw cycles

Consolidated undrained triaxial shear tests on thawed saturated clay with different initial compaction degrees were conducted under different strain rates and confining pressures to study the effect of strain rates on the mechanical properties of the thawed saturated clay. The stress-strain characteristic curve, pore water pressure, secant modulus (E₅₀), peak strength, residual strength and shear strength index of thawed saturated clay were analyzed. The results show that when the strain rate increases, the peak and residual strengths of the saturated clay first increase then decrease, then continue to increase; but the secant modulus E₅₀ increases continuously. The strain rate does not change the strain magnitude corresponding to the deviatoric stress peak. The initial compaction does not affect the strain value corresponding to the peak strength of the thawed saturated clay. And the initial compaction degree has little effect on the development trend of pore water pressure of thawed saturated clay at confining pressure of 120 kPa and strain rate of 0.15%/h. The effect of initial compaction is significant as the strain rate exceeds 1.5% / h. The confining pressures have great impact on the developments of the pore water pressures and the strain values at the peak strengths. With the increase of confining pressure, the strain value and the pore water pressure corresponding to the peak strength of the thawed saturated clay increase. Internal fraction angles decrease with the increase of strain rates when the strain rates slower than 15%/h, but increase with the increasing strain rates when the strain rates exceed 15%/h. Cohesion of the thawed saturated clay increases with the increase of strain rates. The results of this study imply theoretical significance to understand the effect of increasing the strain rate of molten soil.